Polycarbonates are well known and have been widely employed for the production of thermoplastic molded articles.
Polycarbonate derived from bisphenol-A is a high-performance plastic with good impact strength. In addition to ductility (impact strength), general-purpose polycarbonate has high transparency, wide temperature limits (high impact resistance below -60.degree. C. and a UL thermal endurance rating of 115.degree. C. with impact), good dimensional stability, high creep resistance and electrical properties which qualify it as sole support for current carrying parts (up to 125.degree. C. without loss of impact strength).
Flame retardant polycarbonates have a wide range of applications. Polycarbonates are rendered flame retardant by a host of various additives. Some of these additives detrimentally affect one or more of the physical properties of polycarbonates.
A particularly effective flame retardant polycarbonate is a chlorine containing bisphenol polycarbonate in which the phenol moieties of the bisphenol are linked in the 1,1- positions to 2,2-dichloroethylene. These chlorine containing bisphenol polycarbonates have very good resistance to burning and smoke formation while retaining the physical properties of polycarbonates. However, these chlorine containing bisphenol polycarbonates require high processing temperatures and, at these temperatures, thermal cracking may result in loss of chlorine and a viscosity buildup and degradation of the composition. This degradation is shown by color formation and mold corrosion. Also, these chlorine containing bisphenol polycarbonates exhibit U.V. unstability.